Expansion tank issue

[alxy]

Hi bros,When I used to open my expansion tank in the mornings (i.e. when engine cold), I see the indicator stalk up to the "max" position, meaning water is full and I can also clearly see the water level in the tank.However, after I changed my expansion tank recently, now when I open the cap, the stalk is nowhere to be seen (i.e. it has dropped low into the tank). Only when I release the bleeder screw, the water level goes up until the stalk is up to the "max" position like before.So wanna ask, which situation is the normal one? Was it before or now? When I release the bleeder screw, is it the water coming back to the tank or is the release of pressure sucking more water out of my radiator to the tank? Bottom-line, I wanna know if this means I have a leak now, or water in my radiator is OK.Thanks!

 

[ezzo369]

It's normal. if you look carefully at the expansion tank, there should be a dash mark ( -----) and a label "KALT". Your radiator water should be in this position when in Cold / Kalt. BMW uses vacuum system. so when you open the bleed screw, the water will raise as the system is no longer in a vacuum state. same thing will happen when you running your engine with an opened engine oil cap - it will not run smoothly

 

[alxy]

Actually I got my answer later this morning. After running the car a while, I got my temperature needle in the red zone. Had to stop for a while to let it cool down. Then fill back up with water. So looks like releasing the bleed screw sort of like creates some pressure that sucks in water from the radiator to the expansion tank, thereby emptying the radiator. So I guess I still have some leak somewhere. My problems are only starting.....

 

[jarance]

Alxy, did your mechanic bleed the radiator when it was replaced.

and did you change all the hoses and thermostat as well. btw, which model is you ride?

 

[alxy]

Long story actually. Tank cracked some time back and I did not have time to drive to regular mech Ah Meng at MSpeed. So I took car to nearest decent looking workshop. They appear to struggle a bit when fixing back the tank. Though they did do the whole bleeding process. After that, I found like the tank was slanting a bit and radiator not quite straightened up. Probably because of that, new tank also leaked quite a bit (can clearly see underside of car dripping water). So took it to MSpeed and got that sorted out. No obvious leak now, but have to fill it up every 3-4 days or so (about 1 litre each time). Ah Meng pressure tested it and found no apparent problems. So it's probably a slow leak somewhere. Latest thing I did was change the tank cap few days back. Thought that might help. But looks like still no good. Hoses not changed, so that's what I suspect next. Might be some connector rusted or hairline cracked. Worst case scenario is radiator cracked

Mine is 2001 325

 

[ICEMAN 68]

i've read somewhere about the stalk is that, when the colour tends to change to a lighter colour , it's time for you to change the entire expansion unit ....

dark coloured stalk -- still new
fadded coloured stalk --- time has come to change the entire unit ...

 

[B33mEr]

Actually I got my answer later this morning. After running the car a while, I got my temperature needle in the red zone. Had to stop for a while to let it cool down. Then fill back up with water. So looks like releasing the bleed screw sort of like creates some pressure that sucks in water from the radiator to the expansion tank, thereby emptying the radiator. So I guess I still have some leak somewhere. My problems are only starting.....

I suspect it was not bleeded properly hence there's air pocket in the radiator system ...

 

[jarance]

Long story actually. Tank cracked some time back and I did not have time to drive to regular mech Ah Meng at MSpeed. So I took car to nearest decent looking workshop. They appear to struggle a bit when fixing back the tank. Though they did do the whole bleeding process. After that, I found like the tank was slanting a bit and radiator not quite straightened up. Probably because of that, new tank also leaked quite a bit (can clearly see underside of car dripping water). So took it to MSpeed and got that sorted out. No obvious leak now, but have to fill it up every 3-4 days or so (about 1 litre each time). Ah Meng pressure tested it and found no apparent problems. So it's probably a slow leak somewhere. Latest thing I did was change the tank cap few days back. Thought that might help. But looks like still no good. Hoses not changed, so that's what I suspect next. Might be some connector rusted or hairline cracked. Worst case scenario is radiator cracked

Mine is 2001 325

If you have not change the hoses. better change it. I have previously change the front and bottom hose but did not change the hose at the engine bay.
I have to top up like 1 litre every 500KM. change the hose recently and the water level have not after I have travel 500KM.
Still monitoring the water level every week before can decided the problem is rectify.

BTW, big job to change the hose mounted at the engine. need to remove fire wall, intake manifold, fuel rail and injector.

hose item 6 and 8

Cooling System Water Hoses - BMW parts catalog

 

[alxy]

Thanks. Will get it checked up next service. Hope nothing goes before then That's one of the bad things about UDM. The worry that something is going to fail and leave you stranded on the road....

 

[redhybrid]

jarance,

is the small tank (left side or the radiator) is what we call expansion tank? Im sorry, just wanna ask why it needs changed. LOL...my backround is proton....never change that one!!

cheers bro..jangan marah!

 

[jarance]

jarance,

is the small tank (left side or the radiator) is what we call expansion tank? Im sorry, just wanna ask why it needs changed. LOL...my backround is proton....never change that one!!

cheers bro..jangan marah!

Yes that is the expansion tank. it is made from abs material. you need to change it every four to five years. One clear sign to change is when you need to top up the coolant every week.
When changing the expansion tank change also the hoses as well.